Conveying devices, such as escalators and moving walkways, for persons are in general known and efficient items of equipment for transportation of persons. Escalators are typically used for the transport of person in vertical direction, for example from one storey of a building to another storey, whereas moving walkways are mostly used for the transport of persons in horizontal direction or at a slight inclination up to 12 degrees from one point to another point. The length and width of the conveying device for persons are selected in dependence on the anticipated passenger traffic for the respective application.
Escalator steps and plates are conceived as single-part or multi-part components and are usually produced by a casting, extruding or forging method. The upper side of the tread elements of steps and plates has a tread pattern in the form of a row of parallel ribs or webs extending from the front side to the rear side of the tread element. The ribs thus extend in the intended direction of movement of the step or plate. In the case of escalator steps, the riser elements thereof also have ribs which usually connect with the ribs of the tread elements. Moreover, the ribs are dimensioned for engagement in comb structures at the threshold regions of the escalator or moving walkway.
Several steps are connected by way of at least one traction means to form a step belt of an escalator. In the same way, several plates are joined together to form a plate belt. A moving walkway or an escalator usually comprises a support structure with two deflecting regions, between which the plate belt or step belt is guided to circulate.
If the plates or steps are produced from cast or diecast aluminium or another suitable metal or metal alloy in one piece an extensive set of moulds has to be available, since every width of the plate belt or step belt requires an individual mould tool. However, mould tools for plates and steps are very expensive. Moreover, the size of these moulded parts, particularly the tread element with its ribs can lead to problems in casting, particularly to formation of shrink holes, so that for avoidance thereof a costly temperature control of the mould tools is necessary.
WO 0066476 A proposes, for solution of this problem, a modular construction of steps and plates so that the different widths of steps or plates can be produced by means of a few and smaller mould tools. The step or plate substantially consists of an extruded support body of aluminium and of a tread element. The tread element comprises a plurality of sub-elements. These sub-elements are fastened to the support body by means of a groove-and-key connection. A first disadvantage of this solution is that mounting of the sub-elements on the support body by lateral pushing of the keys into the grooves can be a difficult and time-consuming process, since the key-and-groove connections have a tendency to cant particularly at the start of pushing in. A second disadvantage of this solution is that the proposed groove-and-key connection has slight play, so that due to vibrations unpleasant noises can arise as a consequence of relative movements between the tread plate and the support body, since the keys are spread in the grooves only at the abutment locations between two tread elements and therefore the play between groove and key is eliminated only at these places.